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/**
 * Copyright (c) 2014, Sindice Limited. All Rights Reserved.
 *
 * This file is part of the SIREn project.
 *
 * SIREn is a free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version.
 *
 * SIREn is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public
 * License along with this program. If not, see .
 */
package com.sindicetech.siren.search.node;

import java.io.IOException;

import org.apache.lucene.index.Term;
import org.apache.lucene.index.Terms;
import org.apache.lucene.index.TermsEnum;
import org.apache.lucene.search.RegexpQuery;
import org.apache.lucene.util.AttributeSource;
import org.apache.lucene.util.ToStringUtils;
import org.apache.lucene.util.automaton.Automaton;
import org.apache.lucene.util.automaton.BasicOperations;
import org.apache.lucene.util.automaton.CompiledAutomaton;

/**
 * A {@link MultiNodeTermQuery} that will match terms against a finite-state
 * machine.
 *
 * 

* * This query will match documents that contain terms accepted by a given * finite-state machine. The automaton can be constructed with the * {@link org.apache.lucene.util.automaton} API. Alternatively, it can be * created from a regular expression with {@link RegexpQuery} or from * the standard Lucene wildcard syntax with {@link NodeWildcardQuery}. * *

* * When the query is executed, it will create an equivalent DFA of the * finite-state machine, and will enumerate the term dictionary in an * intelligent way to reduce the number of comparisons. For example: the regular * expression of [dl]og? will make approximately four comparisons: * do, dog, lo, and log. */ public class NodeAutomatonQuery extends MultiNodeTermQuery { /** the automaton to match index terms against */ protected final Automaton automaton; protected final CompiledAutomaton compiled; /** term containing the field, and possibly some pattern structure */ protected final Term term; /** * Create a new AutomatonQuery from an {@link Automaton}. * * @param term Term containing field and possibly some pattern structure. The * term text is ignored. * @param automaton Automaton to run, terms that are accepted are considered a * match. */ public NodeAutomatonQuery(final Term term, final Automaton automaton) { super(term.field()); this.term = term; this.automaton = automaton; this.compiled = new CompiledAutomaton(automaton); } @Override protected TermsEnum getTermsEnum(final Terms terms, final AttributeSource atts) throws IOException { return compiled.getTermsEnum(terms); } @Override public int hashCode() { final int prime = 31; int result = super.hashCode(); if (automaton != null) { // we already minimized the automaton in the ctor, so // this hash code will be the same for automata that // are the same: int automatonHashCode = automaton.getNumberOfStates() * 3 + automaton.getNumberOfTransitions() * 2; if (automatonHashCode == 0) { automatonHashCode = 1; } result = prime * result + automatonHashCode; } result = prime * result + ((term == null) ? 0 : term.hashCode()); return result; } @Override public boolean equals(final Object obj) { if (this == obj) return true; if (!super.equals(obj)) return false; if (this.getClass() != obj.getClass()) return false; final NodeAutomatonQuery other = (NodeAutomatonQuery) obj; if (automaton == null) { if (other.automaton != null) return false; } else if (!BasicOperations.sameLanguage(automaton, other.automaton)) return false; if (term == null) { if (other.term != null) return false; } else if (!term.equals(other.term)) return false; return true; } @Override public String toString(final String field) { final StringBuilder buffer = new StringBuilder(); buffer.append(this.getClass().getSimpleName()); buffer.append(" {"); buffer.append('\n'); buffer.append(automaton.toString()); buffer.append("}"); buffer.append(ToStringUtils.boost(this.getBoost())); return buffer.toString(); } }





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